Commander..There has been certain instances where 1 ammo/oil refinery was placed on top of another ,,When this happens 1 ammo/oil is obstructed from view,,The way to correct this is to "edit" your base..Look on the right lower side of game screen,,click on the arrow and just move your ammo/oil ref. around ..If the 6th bldg appears ...just place carefully on the base where you desire them to be,,again..just make sure that you do not place 1 on top of the other,,,(it shouldn't work if you did,,but for some odd reason several has had that to happen..and they found them after they moved base structures around )